<template>
    <div class="list">
        <div
            class="item"
            v-for="item of letters"
            :key="item"
            :ref="item"
            @touchstart ="headertouchStatus"
            @touchmove = "headertouchMove"
            @touchend = "headertouchEnd"
            @click="changClick"
        >{{item}}</div>
    </div>
</template>

<script>
/* eslint-disable */
export default {
    name: 'cityAlphabet',
    props: {
        cities : Object
    },
    data(){
        return {
            touchStatus: false,
            startY: 0,
            timer: null
        }
    },
    updated (){
        this.startY = this.$refs['A'][0].offsetTop
    },
    computed: {
        letters() {
            const letters = []
            for (let i in this.cities){
                letters.push(i)
            }
            return letters
        }
    },
    methods:{
        changClick(e) {
            this.$emit('change', e.target.innerText)
        },
        headertouchStatus(){
            this.touchStatus = true
        },
        headertouchMove(e){
            if(this.timer){
                clearTimeout(this.timer)
            }
            this.timer = setTimeout(()=>{
                if(this.touchStatus){
                    const touchY = e.touches[0].clientY - 81
                    const index = Math.floor((touchY - this.startY) / 20)
                    if(index >= 0 && index < this.letters.length){
                        this.$emit('change',this.letters[index])
                    }
                }
            },16)
        },
        headertouchEnd(){
            this.touchStatus = false
        }
    }
}
</script>

<style lang="stylus" scoped>
    @import '~styles/varibles.styl';
    .list
        display flex
        flex-direction column
        justify-content center
        position absolute
        top 1.62rem
        right 0
        bottom 0
        width .44rem
        .item
            text-align center
            line-height .4rem
            color $bgColor
</style>
